Production of (2S,3S)-2,3-butanediol and (3S)-acetoin from glucose using resting cells of Klebsiella pneumonia and Bacillus subtilis

Production of highly pure (2S,3S)-2,3-butanediol ((2S,3S)-2,3-BD) and (3S)-acetoin ((3S)-AC) in high concentrations is desirable but difficult to achieve. In the present study, glucose was first transformed to a mixture of (2S,3S)-2,3-BD and meso-2,3-BD by resting cells of Klebsiella pneumoniae CICC 10011, followed by biocatalytic resolution of the mixture by resting cells of Bacillus subtilis 168. meso-2,3-BD was transformed to (3S)-AC, leaving (2S,3S)-2,3-BD in the reaction medium. Using this approach, 12.5 g l(-1) (2S,3S)-2,3-BD and 56.7 g l(-1) (3S)-AC were produced. Stereoisomeric purity of (2S,3S)-2,3-BD and enantiomeric excess of (3S)-AC was 96.9 and 96.2%, respectively.     

Fiber surface characterization of old newsprint pulp deinked by combining hemicellulase with laccase-mediator system

Deinking of old newsprint (ONP) by combining hemicellulase with laccase-mediator system (LMS) was investigated, and surface chemical composition and fiber morphology changes during the deinking process were studied by electron spectroscopy for chemical analysis (ESCA), contact angle (CA), attenuated total reflectance fourier transform infrared spectrometry (ATR-FTIR), fiber quality analyzer (FQA), and environmental scanning electronic microscopy (ESEM). Results showed that, compared to the pulp deinked with hemicellulase or LMS individually, effective residual ink concentration (ERIC) was lower for the hemicellulase/LMS-deinked pulp. This indicated that there is a synergistic deinking effect between hemicellulase and LMS. It was found that O/C ratio of the fiber surface increased and the surface coverage of lignin decreased during the hemicellulase/LMS deinking process. The contact angle of the hemicellulase/LMS-deinked pulp was lower than that of pulps deinked with each individual enzyme. ESEM observations showed that more fibrils appeared on the fiber surface due to synergistic treatment.     

Activation of M3 muscarinic receptors inhibits T-type Ca(2+) channel currents via pertussis toxin-sensitive novel protein kinase C pathway in small dorsal root ganglion neurons

Cobrotoxin (CbT), a short-chain postsynaptic α-neurotoxin, has been reported to play a role in analgesia. However, to date, the detailed mechanisms still remain unknown. In the present study, we identify a novel functional role of CbT in modulating T-type Ca²⁺ channel currents (T-currents) in small dorsal root ganglia (DRG) neurons as well as pain behaviors in mice. We found that CbT inhibited T-currents in a dose-dependent manner. CbT at 1 μM reversibly inhibited T-currents by ~ 26.3%. This inhibitory effect was abolished by the non-selective muscarinic acetylcholine receptor (mAChR) antagonist atropine, or the selective M3 mAChR antagonist 4-DAMP, while naloxone, an opioid receptor antagonist had no effect. Intracellular infusion of GDP-β-S or pretreatment of the cells with pertussis toxin (PTX) completely blocked the inhibitory effects of CbT. Using depolarizing prepulse, we found the absence of direct binding between G-protein βγ subunits and T-type Ca²⁺ channels in CbT-induced T-current inhibition. CbT responses were abolished by the phospholipase C inhibitor U73122 (but not the inactive analog U73343). The classical and novel protein kinase C (nPKC) antagonist chelerythrine chlorid or GF109203X abolished CbT responses, whereas the classical PKC antagonist Ro31-8820 or inhibition of PKA elicited no such effects. Intrathecal administration of CbT (5 μg/kg) produced antinociceptive effects in mechanical, thermal, and inflammatory pain models. Moreover, CbT-induced antinociception could be abrogated by 4-DAMP. Taken together, these results suggest that CbT acting through M3 mAChR inhibits T-currents via a PTX-sensitive nPKC pathway in small DRG neurons, which could contribute to its analgesic effects in mice.     

Mechanistic insight of photo-induced aggregation of chicken egg white lysozyme: the interplay between hydrophobic interactions and formation of intermolecular disulfide bonds

Recently, it was reported that ultraviolet (UV) illumination could trigger the unfolding of proteins by disrupting the buried disulfide bonds. However, the consequence of such unfolding has not been adequately evaluated. Here, we report that unfolded chicken egg white lysozyme (CEWL) triggered by UV illumination can form uniform globular aggregates as confirmed by dynamic light scattering, atomic force microscopy, and transmission electron microscopy. The assembling process of such aggregates was also monitored by several other methods, such as circular dichroism, fluorescence spectroscopy, mass spectrometry based on chymotrypsin digestion, ANS-binding assay, Ellman essay, and SDS-PAGE. Our finding is that due to the dissociation of the native disulfide bonds by UV illumination, CEWL undergoes drastic conformational changes resulting in the exposure of some hydrophobic residues and free thiols. Subsequently, these partially unfolded molecules self-assemble into small granules driven by intermolecular hydrophobic interaction. With longer UV illumination or longer incubation time, these granules can further self-assemble into larger globular aggregates. The combined effects from both the hydrophobic interaction and the formation of intermolecular disulfide bonds dominate this process. Additionally, similar aggregation behavior can also be found in other three typical disulfide-bonded proteins, that is, α-lactalbumin, RNase A, and bovine serum albumin. Thus, we propose that such aggregation behavior might be a general mechanism for some disulfide-bonded proteins under UV irradiation.     

Highly selective c-Jun N-terminal kinase (JNK) 3 inhibitors with in vitro CNS-like pharmacokinetic properties II. Central core replacement

In this Letter, we describe the evolution of selective JNK3 inhibitors from 1, that routinely exhibit >10-fold selectivity over JNK1 and >1000-fold selectivity over related MAPKs. Strong SAR was found for substitution of the naphthalene ring, as well as for inhibitors adopting different central scaffolds. Significant potency gains were appreciated by inverting the polarity of the thione of the parent triazolothione 1, resulting in potent compounds with attractive pharmacokinetic profiles.     

抗吡虫啉单克隆抗体的制备及鉴定

为制备灵敏度高,特异性强的抗吡虫啉单克隆抗体,建立经济、快速、准确的吡虫啉残留免疫学分析方法,采用分子模拟技术分析吡虫啉及其类似农药的电荷分布后,选择1-[6-(2-羧乙硫基-3-吡啶)甲基]-N-硝基-2-咪唑啉亚胺 (H1) 作为免疫半抗原,1-(6-氯-3-吡啶甲基)-3-羧丙基-N-硝基-2-咪唑啉亚胺 (H2) 作为包被半抗原,利用NHS酯法将H1和H2分别与牛血清蛋白 (BSA) 和卵清蛋白 (OVA) 偶联合成免疫原与包被原。免疫BALB/c小鼠后,采用常规杂交瘤技术共获得2株稳定分泌抗吡虫     

Crystal structure of a human cleavage factor CFI(m)25/CFI(m)68/RNA complex provides an insight into poly(A) site recognition and RNA looping

Cleavage factor I(m) (CFI(m)) is a highly conserved component of the eukaryotic mRNA 3' processing machinery that functions in sequence-specific poly(A) site recognition through the collaboration of a 25 kDa subunit containing a Nudix domain and a larger subunit of 59, 68, or 72 kDa containing an RNA recognition motif (RRM). Our previous work demonstrated that CFI(m)25 is both necessary and sufficient for sequence-specific binding of the poly(A) site upstream element UGUA. Here, we report the crystal structure of CFI(m)25 complexed with the RRM domain of CFI(m)68 and RNA. The CFI(m)25 dimer is clasped on opposite sides by two CFI(m)68 RRM domains. Each CFI(m)25 subunit binds one UGUA element specifically. Biochemical analysis indicates that the CFI(m)68 RRMs serve to enhance RNA binding and facilitate RNA looping. The intrinsic ability of CFI(m) to direct RNA looping may provide a mechanism for its function in the regulation of alternative poly(A) site selection.     

Synthesis, antibacterial activities and molecular docking studies of Schiff bases derived from N-(2/4-benzaldehyde-amino) phenyl-N'-phenyl-thiourea

A series of novel Schiff base derivatives have been designed and synthesized, and their biological activities were also evaluated as potential inhibitors of FabH. These compounds were assayed for antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus. Compounds with potent antibacterial activities were tested for their E. coli FabH inhibitory activity. Compound 3v showed the most potent antibacterial activity with MIC of 1.56-6.25 μg/mL against the tested bacterial strains and exhibited the most potent E. coli FabH inhibitory activity with IC(50) of 4.3 μM. Docking simulation was performed to position compound 3v into the E. coli FabH active site to determine the probable binding conformation.     

Fen1 mutations that specifically disrupt its interaction with PCNA cause aneuploidy-associated cancer

DNA replication and repair are critical processes for all living organisms to ensure faithful duplication and transmission of genetic information. Flap endonuclease 1 (Fen1), a structure-specific nuclease, plays an important role in multiple DNA metabolic pathways and maintenance of genome stability. Human FEN1 mutations that impair its exonuclease activity have been linked to cancer development. FEN1 interacts with multiple proteins, including proliferation cell nuclear antigen (PCNA), to form various functional complexes. Interactions with these proteins are considered to be the key molecular mechanisms mediating FEN1's key biological functions. The current challenge is to experimentally demonstrate the biological consequence of a specific interaction without compromising other functions of a desired protein. To address this issue, we established a mutant mouse model harboring a FEN1 point mutation (F343A/F344A, FFAA), which specifically abolishes the FEN1/PCNA interaction. We show that the FFAA mutation causes defects in RNA primer removal and long-patch base excision repair, even in the heterozygous state, resulting in numerous DNA breaks. These breaks activate the G2/M checkpoint protein, Chk1, and induce near-tetraploid aneuploidy, commonly observed in human cancer, consequently elevating the transformation frequency. Consistent with this, inhibition of aneuploidy formation by a Chk1 inhibitor significantly suppressed the cellular transformation. WT/FFAA FEN1 mutant mice develop aneuploidy-associated cancer at a high frequency. Thus, this study establishes an exemplary case for investigating the biological significance of protein-protein interactions by knock-in of a point mutation rather than knock-out of a whole gene.